That varied.
Over time and space – and sadly for description – not ever uniformly. Trying such a broad stroke nevertheless: Until the 1940s it went up and down at the same time and this differed between locations, social strata. While extremely poor and remote populations started to wear it, in urban contexts its use went down. But even in rural areas it was very different for example between Tashkent and Samarkand.
What was considered 'Islamic dress' or traditional dress, and thus 'appropriate', 'modest' etc, was never really uniform and came in variations:

Uzbek women at the beginning of the 20th century. Two of them wear the traditional burqa (Paranji). Photo purchased during my stay in Samarkand in a small post office.
–– Sara Maniscalco: "Cotone Di Stato. Sfruttamento del lavoro e risorse naturali nella Repubblica dell’Uzbekistan", Tesi di Laurea Magistrale, Università degli Studi di Milano Bicocca, 2015. (PDF)
In 1927 this "attack" was the party line. "All veils down immediately!" Projected to be concluded within six months, tops.
Making it also a great symbol to resist sovietisation.
Being a member of the party had as prerequisite unveiling. But unveiled women were also murdered by traditionalists.
Becoming a proper liberated Soviet Uzbek woman looked like this

Komsomols (Communist Youth Leaguers) organized at the Regional Uzbek Women and Girls' House of Knowledge. Photo from Uzbek women's Magazine Yangi Yo'l (1926)
–– Marianne R. Kamp: "Three Lives of Saodat: Communist, Uzbek, Survivor", The Oral History Review, Vol. 28, No. 2, 2001, pp21–58.
On the highest level and after 12 months into this project Lenin's widow argued that this was asking too much too fast and the 'efforts' slowed down, abandoned the use of public force. Party officials now working with incentives and arguments instead of force.
During the 1930s the veil and other traditional clothing items came out of fashion to a degree, but they were still much too widely visible for communist party's comfort.
Going out, of the house, as such, and going to school, as such, were already signs of defying traditional society and thus both increased the likelihood of doing that unveiled. But not entirely in the early years. Factories had an easy time. Women going to work were already more modern and health and safety regulations made prohibition of that dress just mandatory.

–– Women in a factory processing cotton, Uzbek SSR.
To describe the situation shortly after hujum began:
In Bukhara, the OGPU reported that Adolat Burkhanova, age eighteen, was murdered by her husband on the street four days after Bukhara’s first mass unveiling, on March 8, 1928. Her husband, a Party candidate, forbade her to enter school, but she tried to enroll anyway and he killed her.
In Tuda-Maidon, an ishon collected false evidence about the wife of a village council representative, a woman who unveiled on March 8, trying to demonstrate that she was a prostitute. Under this pressure, she re-veiled.
A student at the Tashkent Medical Technical School, Pulatova, committed suicide because her classmates insulted her, calling her a prostitute for unveiling. Family members of unveiled women also had to endure these aspersions. Some of the murders of women were undoubtedly responses to public, social stigma, and shame; that is, they were attempts to restore family honor by killing women who were blamed for bringing shame on themselves and their relatives. Inability to cope with the public stigma of unveiling affected men as well as women. Some men divorced unveiled wives, and in Bukhara a shoemaker committed suicide because his wife unveiled.
Throughout the first months of 1929, meetings for activists, council election campaigns, and union meetings all involved discussions of a ban on veiling. At the Central Asian Communist University in Tashkent, women activists circulated petitions in favor of an anti-veiling decree; Rahbar-oi remembered signing one. Yangi Yo’l’s editors were avid supporters of a decree; the journal published many accounts of meetings and demonstrations favoring the anti-veiling law and tried to make this campaign seem widely popular. Their coverage was so one-sided that they did not even address anti-decree arguments or acknowledge widespread anti-unveiling attitudes. Qizil O’zbekiston articles recalled the large numbers of women activists murdered in 1928, and demanded that a law against veiling be enacted in their memory. When the Third Congress of Soviets of Uzbekistan opened in April 1929, Saodat Shamsieva, a Komsomol member, marched down the main avenue in Samarkand with a column of women who were carrying signs and banners for an unveiling decree. As a Komsomol representative, she gave a speech to the congress, asking for a decree.
In mid-April 1929, the congress indirectly rejected the proposed unveiling decree.
(Kamp)
During the war this then changed as Soviet Central Asia saw a large influx from other areas of the SU, mostly from the West: Russians, Germans, Jews, whether deported, resettled, or migrating there for work. This russified the society to a bigger degree than all other campaigns.
During the 1940s the more idealised women's headgear was the something like this:
-- Four lady pilots of the Uzbek SSR in their flight suits.
And in education:

–– Talabalar yangi oʻzbek kirill alifbosi bilan tanishmoqda. Toshkent, 1943-yil. (Getting to know the new Cyrillic alphabet)
In cities the veil was already rare during the late forties and almost without any public support by the beginning of the sixties.
Indeed some wives of party officials were also seen veiled at times after 1928. But during the 30s it also saw a backlash that poorer and more rural communities saw more veils.
In villages around Parkent, some communities had mass unveilings along with organizational meetings for collective farms. In others, women unveiled more gradually, during the 1930s, as they faced increasing pressure to go out and work in the fields, and several farmers remembered that women on their collective farms unveiled after World War II. In the small city of Parkent, by contrast, many women were still wearing paranjis in the 1950s. During one interview with an elderly collective farm woman there, women guests at her feast talked about unveiling in the 1950s. One such guest, who had been a teenager and a Komsomol member, told me that in the 1950s her parents made her start wearing the paranji when they with- drew her from school at age sixteen to arrange a marriage for her. She wore her paranji for one year following her marriage, because her husband wanted her to, but then government officials held a public unveiling meeting and she stopped wearing her paranji.
L. U., from a very religious family in Shahrisabz, said that unveiling agitation took place there in 1928, but that his mother continued wearing the paranji until her death, and until 1960 a number of other women did as well. In his kolkhoz, “based on the view of Islam,” men and women remained separate. Men worked outdoors, while women formed a silkworm and embroidery artel. O. B. said that women were still wearing the paranji during World War II in his village and that the village head told them to unveil in 1954. B. Sh. said that even though eight women unveiled in 1928 at a Hujum meeting, the rest all continued wearing the veil until after World War II: “They would go out covered; they would not go out naked!”
Party attention to veiling and unveiling was inconsistent in the 1930s, with continuing pressure to unveil in some communities and little or none in others. Nonetheless, as the kolkhoz became the most wide-spread organizing factor for rural communities, and as kolkhozes demanded women’s labor, women on most collective farms gradually went to work and also ceased veiling in the paranji.
Kolkhozes built schools, the local Party and government pressured families to send daughters to school, and rural values changed, so that parents saw benefit in sending their children to school. Girls could not veil at school, and this contributed to the paranji’s gradual demise.
Though there was an urban revival in paranji wearing during World War II, which some authors have associated with the increase in religious freedom that Stalin granted during the war, the paranji had become a heavily discouraged choice adopted by few women.
–– Marianne Kamp: "The New Woman In Uzbekistan. Islam, Modernity, and Unveiling under Communism", Washinton University Press: Seattle, London, 2006.
The picture in the question for an entire classroom of girls wearing veil is therefore not really 'impossible', but a bit unlikely for an urban setting. It was very out of fashion by then, but not entirely forbidden and/or entirely suppressed.
Educational setting, according to the Great Soviet Uzbek Encyclopedia (The Bolshevik Sovetskaya Encyclopedia):

–– Слушательницы курсов ликвидации неграмотности. (Students in reading class) 1927.
–– UZBEKSKAYA SOVETSKAYA SOCIALISTIC RESEARCH REPUBLIC

–– An all-girls classroom in the Uzbek SSR, early-mid 20th century

–– [Max Penson: Девушки в классе в Ташкенте. Пенсон начал новую жизнь в Центральной Азии, приступив к работе в качестве учителя рисования.][16]
After 1991 this whole process has swung back again and unveiled women were publicly attacked again.
–– Douglas Taylor Northrop: "Veiled empire: gender and power in Stalinist Central Asia", Cornell University Press: Ithaca, 2004. (p344–357)
Whether the outcome of khudzhum can be viewed as a success is a disputed issue amongst scholars, although the consensus is that it did achieve its objective of unveiling women. A small number of women actively embraced the policy and became members of the Communist Party of Uzbekistan.
–– Sevket Akyildiz & Richard Carlson: "Social and Cultural Change in Central Asia. The Soviet legacy", Routledge: Abingdon, New York, 2014, p41.
–– Paul Stronski: "Tashkent: Forging a Soviet City, 1930–1966", University of Pittsburg Press: Pittsburgh, 2010. p188–201.
The influence of Islam is associated with the appearance of street veils in the form of a robe under various names among the Tajik or Uzbek population, in particular among the Deshtikipchak groups of Uzbek, recorded in the mid-twentieth century, for example, by B. Kh. Karmysheva in the Samarkand, Surkhandar’ia, and Kashkadar’ia oblasts [Samarqand, Surkhondaryo, and Qash-qadaryo violyats in modern Uzbek]. Short white mantles without sleeves, appearing only in the Soviet period, became something of a “school uniform” for upper-grade girls in Shakhrizyabz, but without the face covering.
–– N. P. Lobacheva: "On the History of the Paranja", Anthropology & Archeology of Eurasia, Vol 36, No 2, 1997, pp 63-90.
Online summary at
–– Bradley Farless: "Gender and Modernity in Soviet Central Asia", 23 May 2013.
–– Chika Obiya: "The Politics of the Veil" in the Context of Uzbekistan", Center for Integrated Area Studies, Kyoto University, Japan,
CIAS discussion paper No.63 : Islam and gender in Central Asia --Soviet modernization and today's society, 2016-03. (PDF)